Hilton Davis Chemical Co. v. Warner-Jenkinson Company, Inc.
62 F.3d 1512 (1995)
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Rule of Law:
Patent infringement under the doctrine of equivalents is a question of fact determined by whether the accused product or process contains elements identical or substantially equivalent to each claimed element of the patented invention. The test for equivalency is whether the differences between the claimed invention and the accused device are insubstantial, an objective inquiry which may be guided by the function-way-result test and other relevant evidence.
Facts:
- Hilton Davis Chemical Co. held U.S. Patent No. 4,560,746 for an improved process to purify commercial dyes using ultrafiltration, which replaced an older method known as 'salting out'.
- Claim 1 of the patent specified a process that must operate at a pH 'from approximately 6.0 to 9.0' and under a hydrostatic pressure of 'approximately 200 to 400 p.s.i.g.'
- During the patent application process, Hilton Davis added the specific pH range of 6.0 to 9.0 to distinguish its invention from a prior patent (the Booth patent) that disclosed a similar process operating at a pH above 9.
- Warner-Jenkinson Co., Inc., a competitor, also developed and began using an ultrafiltration process to purify its dyes.
- Warner-Jenkinson's process operated at a pH of 5.0 and at pressures ranging from 200 to nearly 500 p.s.i.g., placing it outside the literal terms of Hilton Davis's patent claim.
- Warner-Jenkinson developed its process independently, without knowledge of the '746 patent, until after it had already begun commercial use of the process.
Procedural Posture:
- Hilton Davis Chemical Co. sued Warner-Jenkinson Co., Inc. in the U.S. District Court for the Southern District of Ohio for patent infringement.
- Following a nine-day trial, a jury returned a verdict finding that the patent was not invalid and that Warner-Jenkinson had infringed under the doctrine of equivalents.
- The jury also found the infringement was not willful and awarded damages.
- The district court denied Warner-Jenkinson's post-trial motions and entered a permanent injunction.
- Warner-Jenkinson appealed the judgment to the U.S. Court of Appeals for the Federal Circuit.
- After a panel heard oral argument, the full court voted to rehear the appeal en banc to resolve key questions about the doctrine of equivalents.
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Issue:
Is a product or process that does not literally meet the terms of a patent claim nonetheless infringing under the doctrine of equivalents if the differences between it and the claimed invention are insubstantial?
Opinions:
Majority - Per Curiam
Yes. A product or process that does not literally infringe is nonetheless infringing under the doctrine of equivalents if the differences between it and the claimed invention are insubstantial. The core test for the doctrine is the 'insubstantial differences' standard, assessed from the perspective of a person of ordinary skill in the art. While the traditional function-way-result test is a useful tool for this analysis, it is not the sole test. Other objective evidence is relevant, including the known interchangeability of the components, evidence of copying (which suggests insubstantial differences), and evidence of 'designing around' the patent (which suggests substantial differences). Infringement under the doctrine is a question of fact to be decided by the jury, not an equitable remedy applied at the court's discretion. Here, substantial evidence supported the jury's finding that Warner-Jenkinson's process, despite operating at a pH of 5.0 and pressures up to 500 p.s.i.g., was insubstantially different from the claimed invention. Prosecution history estoppel does not bar the claim, as the pH range was added to distinguish art operating above pH 9, not to surrender the range below pH 6.
Concurring - Newman
I concur with the majority's holding to reaffirm the criteria of Graver Tank and reject a new 'equity' threshold for the doctrine of equivalents. However, I question whether the doctrine is the most effective means to achieve its goal of promoting technologic innovation. The doctrine's application can be unpredictable, creating uncertainty for both innovators and competitors. While the doctrine serves the interest of justice by protecting inventors from minor variations, the technology community and legislature should explore statutory alternatives that might provide greater clarity and predictability for protecting continuing technological developments, potentially reducing the need for such a broad, judicially-created doctrine.
Dissenting - Plager
The doctrine of equivalents is a uniquely equitable remedy that should be applied exclusively by a judge, not a jury. The majority's decision continues to give juries a 'virtually uncontrolled and unreviewable license' to find infringement, which undermines the public notice function of patent claims by making their boundaries unpredictable. The doctrine should be reserved for special cases to prevent a 'fraud on the patent,' not used as a routine second chance for patentees who fail to prove literal infringement. By failing to acknowledge the doctrine's equitable roots and its built-in constraints, the majority abdicates the court's responsibility to police its application and protect the public's right to rely on the clear language of patent claims.
Dissenting - Lourie
I dissent because the district court's instructions to the jury were plainly erroneous under the very standard the majority opinion articulates. The trial judge incorrectly emphasized the function-way-result (FWR) test as the primary analysis, failing to instruct the jury that the ultimate inquiry is the 'substantiality of the differences' between the claimed and accused processes. The FWR test is particularly inadequate for chemical inventions, where structure, not function, is the defining characteristic. The case should be vacated and remanded for a new trial with proper instructions. Furthermore, I believe the applicability of the doctrine is an equitable determination for the court, weighing factors like copying and independent development, before any question is sent to the jury.
Dissenting - Nies
There is no infringement as a matter of law, and the district court should have granted judgment for Warner-Jenkinson. The doctrine of equivalents cannot be used to 'enlarge a patent beyond the scope of its claim.' The patent explicitly claims a pH range of 'approximately 6.0 to 9.0,' and Warner-Jenkinson's process operates at 5.0. This is not a substitution of an equivalent element; it is an expansion of the claim's boundaries. Furthermore, prosecution history estoppel bars Hilton Davis from capturing a pH below 6.0, as the 6.0-9.0 range was a specific limitation added to overcome a prior art rejection. The application of the doctrine of equivalents to undisputed facts is a question of law for the court, not a fact question for the jury.
Analysis:
This en banc decision reaffirmed and clarified the doctrine of equivalents, cementing the 'insubstantial differences' standard as the central inquiry, moving away from a rigid application of the function-way-result test. The court firmly established that determining equivalence is a question of fact for the jury, rejecting the influential argument that it should be treated as an equitable matter reserved for the judge. This holding provides a more flexible, objective framework by allowing other evidence like known interchangeability and designing around, which is crucial for complex technologies. The decision sought to balance patentee protection against the public's need for certainty, though the multiple dissents highlight a deep-seated conflict over whether this standard provides sufficient predictability and respects the public-notice function of patent claims.
